Excessive alcohol consumption has many negative consequences that have been well documented among college students, including thousands of deaths, hundreds of thousands of assaults, and millions of academic consequences. As a result, NIAAA has set a goal to ?Develop and Improve Interventions to Prevent Alcohol Misuse, Alcohol Use Disorder and Alcohol-Related Consequences? with a specific intention to ?Develop and evaluate strategies to prevent and reduce alcohol misuse among young adults, including those in?college.? Fortunately, there are a number of effective interventions that reduce excessive drinking and alcohol-related problems including personalized normative feedback interventions (PNF). In PNF, participants are told how their drinking compares to their perceptions of peer drinking as well as actual peer drinking. When these perceptions are corrected, heavy drinkers reduce their drinking and associated problems. Despite the effectiveness of PNF, there is considerable room for improved understanding of when and for whom PNF works to reduce problematic drinking. This understanding will lead to intervention improvements to further reduce problematic drinking. To work toward NIAAA's goals, we turn to theoretical explanation (i.e., self-determination theory) and more proximal measurement (within-person analyses) to provide an improved understanding of PNF. This project will implement a randomized, controlled PNF intervention for 300 college student heavy drinkers, who will participate in a 2.5 week, ecological momentary assessment to document the effects of the intervention on day-to-day normative perceptions, consumption, and alcohol-related-problems. Data analysis will evaluate the interaction between norms and self-determination at the level of drinking days (i.e., within-persons) and that at the level of the person (between-persons). People who receive the intervention are expected to reduce drinking and alcohol-related problems relative to the control group, but this effect is expected to be particularly strong for those who are lower in self-determination from day-to-day (i.e., within persons) and at baseline (i.e., between-persons). This study will examine how intervention effectiveness is altered by self-determination felt between- and within-persons. The proposed project supports the NIAAA strategic plan's goal of improving interventions to treat alcohol misuse, disorders, and consequences. Through this project, the field will have a better understanding of powerful interventions and predictors of young adult drinking, allowing this problematic drinking to more effectively be addressed and reduced. Through this project and the training associated with conducting it, I will continue to develop as an alcohol researcher, working to use advanced social psychological theory and methodology to increase effectiveness of interventions to reduce problematic alcohol consumption. In conclusion, the award and completion of this project will afford substantial training in ethics, methodologies, statistics, and writing, to a promising young researcher and will address the significant need for innovative research on within-person analysis of the effects of social norms, alcohol consumption, basic theory, and interventions.